Technology advancements are rapidly improving efficiencies and reducing weights for electric power systems. Electric power in both surface and air vehicles has been increasing especially in military and commercial platforms. For example, electric power has replaced pneumatic systems in the Boeing 787, which was specifically designed to be a More Electric Airplane (MEA) with improved energy efficiency.
This trend towards increasing use of electric power systems motivates studies to further improve the efficiency of producing electric power generation in air vehicles with fuel cells. Fuel cells use electro-chemical reactions to produce electricity, waste water, and oxygen-depleted inert gases. Multiple studies have concluded that fuel cells have higher power generation efficiency, compared to jet fuel combustion, gas turbines, and internal combustion engines.
However, regarding aircraft flight fuel efficiency, the increased weight of a fuel cell results in more fuel burned during flight than a gas turbine. Although the weight increase may be partially offset by reducing water loading before flight and recovering fuel cell waste water, the weight penalty must be further reduced to make fuel cell usage more economically attractive.
This could potentially be accomplished by eliminating other aircraft systems that contribute a significant amount of weight. Aircrafts, especially military aircrafts (e.g. C-17A, KC-46A) and transport aircraft (e.g. Boeing 787), use On Board Inert Gas Generation systems (OBIGGS) or Nitrogen Enriched Air (NEA) systems for inerting tanks storing jet fuel. (See “Cobham to Supply Boeing with On-Board Inert Gas Generating System Equipment for US Air Force KC-46 Tanker Program”, Cobham News Release, Ref #461, 1 Aug. 2012; and “Fuel-Tank Safety Comes Standard on New Boeing 787,” copies of these documents are being submitted with an Information Disclosure Statement filed with the present application.). These systems pass air through a semi-permeable membrane to reduce oxygen content and incur a fuel consumption penalty because they use engine bleed air. Engine bleed air incurs a 1% Specific Fuel Consumption (SFC) penalty for each 1 lb./sec of bleed flow. Thus, eliminating the engine bleed for OBIGGS or NEA systems and the systems' weight would provide a large offset for the weight increase with a fuel cell. This disclosed invention also applies to fuel cells used in surface applications to generate where the inert gas can be for fire prevention, fire suppression, preservation of perishables, oxidation prevention, and fumigation.